The present invention relates to a dispensing device for powder material.
In particular, the present invention finds application advantageously in the art field of automatic filling machines equipped with a carousel carrying a plurality of filler heads from which powder material is dispensed into containers.
Each of the aforementioned filler heads comprises a dispensing device designed to direct a given quantity of material by free fall into a relative container positioned on a platform assembly. The platform assembly is equipped with a load cell, located beneath the assembly and connected to the dispensing device, which serves to sense the weight of the container during the fill. Once the load cell senses a predetermined value corresponding to the final filled condition of the container, it will pilot the dispensing device to cut off the flow of powder material.
More exactly, the dispensing device receives the powder material from a vessel by way of a feed duct connected to a bottom end of the selfsame vessel, in such a way that the material can be released by gravity and in measured quantities. In addition, the dispensing device comprises an element located to coincide with an outlet at the bottom end of the duct, by means of which the duct can be closed off selectively.
A first such closure element embraced by the prior art presents a valve consisting in a lever mounted pivotably to a fixed supporting frame. The lever exhibits a substantially circular portion positionable under the outlet in such a way as to close it off completely.
The valve is operated through the agency of a relative linear actuator that shifts the lever by causing it to rotate about the pivot axis. Thus, the circular portion is directed along a path transverse to the longitudinal axis of the duct and into a position under the outlet in such a way as to occlude the selfsame outlet and cut off the flow of powder material.
In reality, the filling method outlined above betrays a drawback connected with the operation of closing the outlet. As the circular portion moves across, in effect, the powder material in flight is diverted and consequently does not drop correctly into the container.
This drawback is attributable to the nature of the movement described by the circular portion, which drags a part of the powder material along the direction of this same movement (transverse to the direction of the flight), diverting it and causing it to spill outside the container. The part of the material not directed into the container thus drops onto the platform assembly, creating problems in the sense that the machine must be cleaned and a proportion of the powder material remains unused.
The prior art also embraces devices that comprise a feed duct extending through an annular chamber. The duct remains fluid-tight with respect to the annular chamber, which is associated with extractor means and caused to draw in air through an annular port coaxial with the outlet of the duct.
Thus, the part of the powder material diverted by the valve is intercepted and aspirated through the port into the annular chamber.
The aspirated material is then returned to the vessel for subsequent reuse.
Even with this second prior art solution however, there is a significant drawback attributable to the constructional complexity of the extraction system. In effect, carousel filling machines are generally equipped with a not inconsiderable number of filler heads. Consequently, if an extraction system of the type previously outlined is to be associated with each of the dispensing devices, this represents an excessive increase in production costs per single filling machine.
A further drawback derives from the fact that the extraction system can be rendered ineffective when the machine is employed to dispense certain powder materials of which the particles are notably heavy. In this instance the particles remain unaffected by the aspirating action, which is not sufficient to counteract the gravitational force that causes the particles diverted away from the container mouth to continue falling.
The object of the present invention is to provide a dispensing device for powder filling machines operating with containers, which will betray none of the aforementioned drawbacks.
In particular, it is an object of the invention to provide a dispensing device for powder filling machines operating with containers, such as will cut off the flow of powder material without any part of the material being scattered outside the container.
The stated object is realized according to the present invention in a dispensing device applicable to machines for filling containers with powder material, comprising a feed duct referable to a longitudinal axis and furnished with at least one outlet from which the powder material is dispensed into a corresponding container; also closure means associated with the outlet, capable of movement between an operating condition in which the outlet is closed to disallow the passage of the powder material, and a non-operating condition in which the outlet remains open
Closure means according to the invention comprise a plurality of occluding elements each capable of movement between a first position corresponding to the operating condition of the closure means, and at least a second position corresponding to the non-operating condition of the closure means. The single occluding element obscures a part of the dispensing outlet when in the first position, and combines with the remaining elements when in the second position to establish a flow section affording a passage to the powder material.